1. Field of the Invention
The present invention relates to a lumbar support device which is incorporated in a seat back of a vehicle seat to support the lumbar portions of an occupant so as to relieve the occupant's fatigue.
2. Description of the Prior Art
Conventionally, in this type of lumbar support device, there are provided in the lower portion of a seat back frame a pair of right and left arms such that they are pivotal forwardly and rearwardly, and between both arms there is extended a lumbar support member comprising of an S spring or the like. When the arms are pivoted, the lower portion of a cushion pad of the seat back is pushed outwardly by means of the support member and to thus adjust the compressive hardness of the lower portion of the cushion pad. In such a manner the supporting pressure applied to the lumbar portions of the occupant can be adjusted.
In the conventional lumbar support device, the support member which extends between both arms is designed to have a predetermined width in a vertical direction. Therefore, in such an arrangement, as the support member is extended with its both ends being fixed to both of these arms respectively and since the support member is pivoted integrally with the arms the upper edge portion of the support member, (which during the pivoting motion is a free end relative to the center of rotation of the arms) is strongly abutted against the cushion pad to push it out on a line in a transverse direction, which brings about a strange and uncomfortable feeling to the occupant.
Also, in an arrangement where the support member is provided such that it is pivotal relative to both arms, when during assembly of the seat back the lower edge portion of a top layer is mounted onto the seat back frame, the lower portion ot the cushion pad is pushed rearwardly and thus the support member is inclined relative to both arms with its lower portion being pushed rearwardly. In this case as well, the upper edge portion of the support member is strongly abutted against the cushion pad to push it out on a line in a transverse direction and, as the result of this, the occupant suffers an uncomfortable and strange feeling.